Weather balloons are used to release radiosondes into the atmosphere. The probes have various sensors and a transmitter that sends the collected data back to Earth. MeteoSwiss releases a weather balloon twice a day: From Monday to Friday, the balloons are launched manually at noon, and automatically at the same time at weekends; the second launch at 11 pm is always automatic. The sounding station is located in Payerne, where data from the atmosphere have been collected since the 1940s.
The hydrogen-filled weather balloons ascend at a speed of around five metres per second, taking approximately two hours to reach an altitude of 30-35 km.